The upper arm contains a single bone (humerus). The forearm contains two bones (radius and ulnar). The wrist has seven small (carpal) bones. The proximal three carpal bones form a joint with the two forearm bones where wrist movement occurs. The distal four form a joint where they meet five metacarpal bones of the hand. [‘Proximal’ is near and ‘distal’ is away from the torso.] Motion is present at the wrist where the base of the thumb (1st metacarpal bone) meets its distal carpal bone. However, there is no movement at the joints of distal carpal bones to the remaining four metacarpal bones because they are tightly connected. The four metacarpal bones meet the phalangeal bones of the fingers to form the metacarpal-phalangeal (MP) joints. The thumb has two phalangeal bones (proximal and distal phalanges) and the long digits have three (proximal, middle and distal phalanges). Moveable joints form between the proximal (MP joint) and middle phalangeal bones as well as the middle (PIP joint) and distal (DIP) phalangeal bones. The carpal tunnel (CT) is a space formed on three sides by the internal surfaces of the wrist bones and inner surface of the transverse carpal ligament (TCL) on the forth side. The TCL is a strong dense ligament under the proximal palm that connects the radial (thumb side) and ulnar (small finger side) wrist bones. The size of the CT is regulated by genetic and environmental factors that influence bone size.
Referring to FIG. 1, FIG. 1 shows a palmar surface 100a of a palm 100b of a hand 100, such as a right or left hand, with horizontal creases 101 and longitudinal creases 201 creases and the skin creases 603 on the respective fingers 606, 607, 608, 609 and the location of the TCL 202. The median nerve is in a tunnel under the TCL 202. The horizontal crease 101 delineates the proximal part 105 of the MP joints 106 and cross the palmar surface 100a where the MP joints 106 flex. The longitudinal skin creases 201 lies in the valley between the thenar muscles 302 on the radial side 301 of the hand 100 and hypothenar muscles 402 on the ulnar side 401 of the hand 100. The longitudinal creases 201 lie over the CT 203. The longitudinal creases 201 are located in the skin where the metacarpal (MC) joint 107 of the thumb 801 flexes to oppose any of the fingers 606, 607, 608, 609 collectively referred to as the long fingers 604. The CT 203 indicated as being located between the dotted 203a and 203b of a distance indicated by the arrow 203c 
Continuing with reference to FIG. 1, the TCL 202 is thickest at its central portion and stabilizes nine flexor tendons that pass through CT 203 (one tendon flexes the thumb 801). The tendons in the CT 203 are wrapped with synovial membranes that form bursae that produce a lubricating substance allowing the tendons to move smoothly to pull the bones in the long fingers 604 and the thumb 801. The median nerve also passes through the tunnel and lies closest to the center of the TCL. The median nerve located in the CT 203 stretches with arm and wrist movement. A problem can result in that the extremes of wrist movement can kink the nerve and tendons where they enter the CT 203.
The shoulder is a ball joint that, allows the upper extremity to move in many directions. The elbow bends to pull (flexion) or push (extension) and rotates the forearm and hand (supination or pronation). Supination is rotation of the forearm to face the palm up. Pronation is rotation of the forearm to face the palm down. The wrist moves up and down (extension or flexion), sideways (radial or ulnar deviation) and in multiple directions by combining these movements.
The thumb 801 has five basic movements. The thumb 801 as a first movement flexes (moves closer) to or as a second movement extends (moves away from) in a direction parallel to the radial side 301 of the hand 100. As a third movement, the thumb 801 abducts or adducts to move up or down perpendicular to the palm 100b. Finally, as a fifth movement, the thumb 801 also opposes or touches any of the long fingers 604. The combination of these movements is called circumduction, which is moving the thumb 801 around in any direction.
The long fingers 604 have three muscle groups working individually or together to flex (pull) the proximal, middle and distal phalangeal bones. One muscle group is in the palm 100b and two muscle groups are in the forearm. The muscles in the palm 100b are the lumbrical muscles. These lumbrical muscles flex the proximal phalanges 606c, 607c, 608c, 609c at the MP joints 106. The lumbrical muscles are relatively small muscles in size.
Further, two other larger muscle groups are located in the front (volar surface) of the forearm and are called the superficial and deep flexor muscles. The superficial flexor muscle is close to the surface of the forearm and the deep flexor muscle lies underneath it. Each flexor forearm muscle is divided into subunits from which four tendons each arise contributing eight tendons that pass through the CT 203. The tendons from the superficial flexor muscle attach to and pull (flex) the middle phalanges 606b, 607b, 608b, 609b. The tendons from the deep flexor muscle attach to and pull the distal phalanges 606a, 607a, 608a, 609a. The deep flexor muscle is larger and stronger than the superficial flexor muscle. All the muscles combine function to sequentially flex the finger bones and produce varying degrees of finger curl to grip various shaped objects. Other muscles in the hand spread the fingers apart or pull them together (abduct or adduct).
When muscle units contract their girth enlarges to pull its smooth cable-like tendon, which in turn pulls its bone at a joint. The amount and strength of finger flexion depends upon the degree of each muscle unit's contraction. This depends on muscle size. Therefore, a larger muscle has greater contractile force. The largest and strongest forearm muscle is the deep flexor, which pull the distal phalangeal bone. Therefore the distal phalanges 606a, 607a, 608a, 609a of the long fingers 604 can exert the most gripping force.
The human hand has the unique ability to hold, grasp and move objects of various sizes, shapes and weight and to provide support to the human body. Handles and handgrips are tools to assist in these functions. Common handles and grips found on canes, bicycle handlebars, sanders, electric and pneumatic and other tools are usually tubular and made of a single size. Long finger bones vary in length. The middle and ring fingers 607 and 608 are longer than the index and small fingers 606 and 609. Because of this size difference, when the long fingers 604 grasp tubular handles the fingertips 610 do not end at the same line. Namely, the fingertip 610 of the small finger 609 ends before the fingertip 610 of index finger 606, which ends before the fingertip 610 of the ring finger 608 and that ends before the fingertip 610 of the middle finger 607 while the thumb 801 overlaps or lies next to the index finger 606.
Usually, the middle phalanges 607b, 608b of the middle finger 607 and the ring finger 608 and the distal phalanges 606a, 609a of the index finger 606 and the small finger 609 exert grip force along the same line on a tubular grip. Therefore, the smaller superficial flexor forearm muscle pulls the middle phalanges 607b, 608b of the middle finger 607 and the ring finger 608 while the deep flexor forearm muscle pulls the distal phalanges 606a, 609a of the index and small fingers 606 and 609, which is asymmetric use of the superficial and deep flexor muscles. Therefore, a problem can develop in that the different flexor muscles pulling different parts of the fingers 606-609 to grip a common handle do not work in concert.
Grip effort depends on brain messages to direct the amount of contraction a muscle segment exerts to the tendon pulling its phalange. The sum of all muscle contraction determines total grip strength. Asymmetrical use of the flexor forearm muscles to the fingers 606-609 limits potential use of the hand 100 to grip and can cause forearm muscle tension.
Such asymmetric use of forearm finger flexor muscles is forced by use of common handles and grips for tools and implements as for heavy equipment, machines, appliances and other devices and can frequently cause problems. This can adversely stress the finger and wrist joints, the contents of the CT 203, the muscles in the hand 100 and forearm and the median nerve. Such stresses are aggravated when common handles are gripped and used in relation to supporting the upper body.
The skin and tissue on the palm 100b and fingers 606-609 is another factor involved in gripping. It contains soft, compressible fatty tissue with tiny but strong perpendicular ligaments extending to the under surface of the skin from deep tissue. These ligaments prevent the skin of the palmar surface 100a from sliding. Aside from cushioning the skin of the fingers 606-609 has ridges and valleys (fingerprints) to enable the hand 100 to grip objects progressively tighter without slipping.
While, various diseases, such as hypothyroidism and diabetes can affect the median nerve in the CT 203, the design method and apparatus of the present invention relates to preventing or reducing traumatic injury and mechanical strain to the hand 100 and wrist. The median nerve in the CT 203 is compressed and flattened under the TCL 202 when the wrist is extended and the fingers 606-609 are forcefully gripping. This occurs, for example, from repeatedly gripping a steering wheel, repetitive vibration from hand sanders, repetitive compression from jackhammers and other forceful activities. These activities can irritate and inflame the median nerve as well as the synovial tissue wrapped around the tendons in the CT 203. The inflamed synovial tissue can swell to compress the median nerve in the CT 203. Scar can form as a result of the inflammation that increases friction to tendon motion in the CT 203. When the contents of the CT 203 are inflamed and the wrist is bent, the pressure in the CT 203 increases exponentially. Aging and repeated injury typically causes the TCL 202 to thicken, which decreases the size of the CT 203. Small size wrists are more prone to repetitive strain and carpal tunnel syndrome (CTS). The symptoms of CTS include wrist pain and finger tingling progressing to loss of sensation and thenar muscle weakness due to compression of the median nerve by the swelled contents of the CT 203.
The wrist works as a fulcrum when a person leans and places their weight on the palm 100b or fingers 606-609 while grasping a common handle to support the upper body. In this position the wrist is generally unsupported. The wrist in this condition maximally extends (bends back) and acts as a fulcrum to support upper body weight, especially when the elbow is straight. Supporting the hand 100 in this way also flattens the palm 100b. Resting the hand 100 on the longitudinal creases 201, in the valley between the thenar muscles 302 and the hypothenar muscles 402, places the weight of the upper body directly on the TCL 202 and transmits pressure to the median nerve which is immediately under it. These positions often produce symptoms of CTS, which could be prevented or reduced by a proper handle or grip.
Efficiency is reached when the parts of the hand 100 work in harmony. The goal of any handle or grip, as well as an objective the present invention is to promote such efficiency. An efficient handle or grip design should maintain the hand 100 in a comfortable position and also avoid placing substantial external pressure on the TCL 202 and reducing internal pressure in the CT 203. A further goal of any handle or grip design, as well as a further objective of the present invention is to facilitate the function of the hand 100 and forearm muscles so they work in concert. Furthermore, such a handle or grip design, as well as a further objective of the present invention should also promote a reduction in the amount of gripping strength typically required to hold a handle or grip. When less gripping strength is used to hold a handle or grip the internal pressure in the CT 203 can be reduced. A handle or grip that fulfills these goals should promote reduced incidence of CTS and repetitive strain disorder.
There are many handgrip patents that fit the hand by being convex and fill in the depression (valley) between the thenar and hypothenar muscle areas, which will pressure the median nerve. Some have depressions fitting the metacarpal and finger pads. For example, U.S. Pat. No. 6,142,918 is listed as a barbell system. U.S. Pat. No. 4,828,261 is listed as a handle for athletic equipment. U.S. Pat. No. 5,556,092 is round with indentations and listed as ergonomic handle. U.S. Pat. No. 5,979,015 is listed as an Ergonomic Hand Grip And Method Of Gripping but the fingertips do not end together to balance grip.
U.S. Pat. No. 5,806,091 is a Hand Grip Aid. This is a pad placed under the web spaces of the long fingers where they meet the skin of the palm. It is held in place by a rubber band or loop. The device merely adds firmness to the web space, where the long fingers lie across a handle as shown on a baseball bat, but the median nerve pressure problem remains.
U.S. Pat. No. 5,873,148 is titled as an Ergonomic Handle System made of four individual pieces that slide along a track on a base handle. Each piece has a groove to accept the finger. The circumferences of the two central pieces are larger than the outer and inner pieces.
U.S. Pat. No. 5,031,640 is titled as a Pad for Preventing Carpal Tunnel Syndrome. It provides a glove padding the thenar area, MP joints and the hypothenar area, and it empties in the region of the CT.
U.S. Pat. No. 6,183,400 is titled as a Hand at Rest Grip. It is designed to reduce gripping force when lifting weights. A ‘palm heel’ (a bulge) is provided to fit the ulnar side of the hand. It spreads to the CT stopping at the longitudinal creases over the median nerve. A strap is placed around the dorsal part of the hand to hold the hand in place. The thumb wraps around a flat bottom. The grip is hinged to attach around a bar for weight lifting. The ‘palm heel’ is curved and concave.
U.S. Pat. No. 5,829,099 is titled as a Universal Ergonomic Handle. It is contoured to match the anatomy of the hand and said to fit the anatomic rest position.
The handle in U.S. Pat. No. 5,761,767 incorporates a flat surface, i.e. “palm heel”, extending from the upper surface of a tube to support the ulnar half of the hand. The object of the handle is to limit wrist movement when lifting weights by using a “hook type hand grip”,
U.S. Pat. No. 5,339,850 discloses an Orthopedic Hand Grip for Ambulation Aids, Tools and Other Implements. The grip includes a ‘palm heel’ extending across the longitudinal crease.